1. Field of the Invention
The present invention is directed to a torsional vibration damper comprising a first damper mass part, a second damper mass part which are rotatable about an axis of rotation, and at least one coupling/damping device by means of which the first damper mass part and the second damper mass part are coupled for torque transmission. The at least one coupling/damping device allows a relative rotation of the first damper mass part and the second damper mass part relative to one another about the axis of rotation. The at least one coupling/damping device acts on the first damper mass part at one of its end regions at a first coupling region and acts on the second damper mass part at its other end region at a second coupling region for transmitting torque between the first damper mass part and the second damper mass part.
2. Discussion of the Prior Art
WO94/10477 discloses a torsional vibration damper of the type mentioned above in the form of a two-mass flywheel for a motor vehicle clutch. This torsional vibration damper has an input part which is coupled with a crankshaft of an internal combustion engine, an output part which is mounted so as to be rotatable by means of a ball bearing at the input part, and a plurality of coupling/damping devices coupling the input part and the output part with one another for common rotation and for transmission of torque. Each coupling/damping device comprises a first coupling member which is mounted in a radial inner region at the output part so as to be swivelable about a coupling axis extending substantially parallel to the axis of rotation of the crankshaft. A second coupling member is connected with the first coupling member at a radial outer portion of the first coupling member so as to be swivelable about a coupling axis extending substantially parallel to the axis of rotation, wherein the radial outer portion of the first coupling member is widened in the circumferential direction. The second coupling member extends approximately in the circumferential direction and is connected at its other end with the input part so as to be swivelable about a coupling axis extending substantially parallel to the axis of rotation of the crankshaft. During a rotation of this known torsional vibration damper, the centrifugal force that is directed outward with respect to the axis of rotation acts on the first coupling member, especially on its widened radial outer region, and tends to orient the first coupling member in a radial outward direction with respect to its articulation point at the output part. When a rotational force is transmitted by this known coupling device, i.e., when a torque is generated between the input part and the output part, the first coupling member is deflected from its radial outwardly oriented rest position by the second coupling part connected with the input part. The extent of deflection is determined, on the one hand, by the centrifugal force which depends on the rate of rotation or speed and, on the other hand, by the torque, i.e., load, to be transmitted between the input part and the output part. That is, with the load remaining equal, a state of equilibrium is introduced in which the first coupling member is deflected from its rest position. If torsional vibrations occur in the drivetrain, this causes the first coupling member of every coupling/damping device to be excited to swivel about its deflection position due to the load alternation vibrations in the torsional vibration damper and accordingly to act as an energy accumulator corresponding to a spring or the like.
In general, the problem in torsional vibration dampers of the type mentioned above is that the component, i.e., the input part, connected with the crankshaft does not rotate exactly in the respective plane associated therewith because bending deformations are generated in the crankshaft, especially by the piston of the internal combustion engine located closest to the input part. These bending deformations lead to a corresponding wobbling movement of the input part about the axis of rotation, accompanied by deflection of the input part out of the associated plane. Since the output part is coupled with the input part by the ball bearing mentioned above so as to be rotatable, but is substantially rigidly coupled therewith with respect to other movements, this wobbling is transmitted to the output part. However, since the output part generally forms a flywheel for a friction clutch in a motor vehicle and a clutch disk coupled with a transmission input shaft is pressed against the flywheel in the engaged state of the clutch, this wobbling can also be transmitted to the transmission input shaft. This can lead to the generation of unwanted vibrations in the drivetrain and can also disadvantageously impair the operability of the entire drivetrain. The bearing support region of the output part at the input part, i.e., the ball bearing, is also stressed to an excessive degree by the enforced wobbling which can lead to damage in this region.